Process of pulping plant tissues by means of a volatile base



Patented Apr. 28, 1931 STATES PATENT OFFICE RALPH MALCOLM HIXON, CHARLES JAMES PETERSON, AND CHESTER HAMLIN WEEK- MAN, 0F AMES, IOWAQASSIGNORS TO IOWA STATE COLLEGE OF AGRICULTURAL AND MECHANICAL ARTS, OF AMES, IOWA, A CORPORATION OF IOWA PROCESS OF PULPING- PLANT TISSUES BY MEANS OF A VOLATILE BASE No Drawing.

This invention relates to the process involved in pulping plant tissues by means of volatile base as distinguished from non-volatile base such as sodium hydroxide which is 5 now generally used for the pulping of plant tissues such as cornstalks, straw and the like.

The principal object of our invention is to provide a process which will reduce plant tissue to a cellulosic pulp, and will permit the 10 recovery of the chemical utilized for pulping the tissue as well as permitting the recovery of both the hemicelluloses and lignins removed from the desired tissue.

By the present process as practiced throughout the world for converting plant tissues into oellulosic pulp, forty to fifty per cent of the original tissue is lost, for instance in the alkali processes, the liquors containing this dissolved material are evaporated and the organic matter burned in order to recover the more valuable alkali used in digesting the material.

In the sulfite process, both the dissolved material and the chemical are treated as sewage, although fermentation of the by drolyzed sugars has been practiced to a very limited extent in Europe. It is estimated that the waste liquors from the annual cellulose production contain at least three million tons of organic matter on a dry basis. If this material were even dried, its fuel value alone would be equivalent to about two mil lion tons of coal.

We have discovered that a volatile base, e. g. ammonium hydroxide, can be substituted for the non-volatile base sodium hydroxide, now used in the process of pulping the tissues (i. e. the grasses). After the tissue has been pulped, the ammonium h droxide can be recovered by distillation. 's the ammonium hydroxide is distilled from the liquors, the organic matter which has been dissolved from the cellulosic tissues separates as a semi-colloidal sludge. This organic matter consists of the lignins and hemicelluloses of the original tissue. Any suitable process could be utilized for converting this organic matter to useful by-products.

As an example of such a process, sheets of paper pulp may be prepared from cornstalks Application filed June 30, 1930. Serial No. 465,058.

or from oat straw by cooking one hundred grams of tissue with one liter of ammonium hydroxide (specific gravity 0.90) for fifteen hours under a pressure of one hundred-pounds per square inch. The temperature of the liquor should be approximately 110 centigrade. The pulp may then be washed and bleached, but received practically no mechanical treatments such as are applied in the production of paper.

This preceding example is illustrative of the principal only and many modifications of the treatment are possible such as the mere moistening of the fiber and then introducing suflicient quantities of the volatile alkali in the gaseous phase to pulp the tissues. The incrusting materials could then be removed with more dilute alkali using a counter-current washing system for maximum efiiciency.

The primary advantage of this process lies not in the actual paper making but in the fact that after the paper is made, the organic matter which, has previously been wasted (about 50% of the original tissue) can be recovered as well as the chemical utilized for pulping the tissue. The organic matter may be converted to useful by-products by any suitable process. For example, after distilling off the ammonia, the hemicelluloses may be hydrolyzed to free sugars or to furfural, the lignin being left as an insoluble residue; or the hemicelluloses may be fermented either with or without previous treatments, the lignins being left as an insoluble residue; or the hemicelluloses and lignins may be jointly converted in the presence of phenolic compounds to resinous bodies.

We claim asour invention:

1. The process of pulping plant tissues, consisting of the subjecting of the plant to a volatile base, the obtaining of the cellulosic materials from the-liquors containing the dissolved material, and the recovery of the volatile base used by distilling the remaining liquors.

The process of pulping plant tissues,

consisting of the subjecting of the plant to a volatile base, the obtaining of the cellulosic materials from the liquors containing the dissolved material, the recovery of the voltile base used by distilling the remaining liquors, and lastly, the obtaining of the remaining 7 organic matter for useful by-products.

3. The'process'of obtaining cellulosic, lig nin and hemicellulose materials from plant tissues consisting in the pulping of the plant by subjecting the same to ammonium hydroxide, the removal of the cellulosic materials from the mass, the removal and recovery of 10 the ammonium hydroxide from the mass, and lastly, the removal and recovery of the lignin and hemicellulose materials from the remaining mass.

4. The process of pulping plant tissues comprising the placement of plant tissue with ammonium hydroxide, the cooking of said plant tissue and ammonium hydroxide under pressure and at a temperature approximately 110 centigrade, the obtaining of the cellulosic pulp from the mass after cooking, the recovery and obtaining of the ammonium hydroxide by distillation, and the recovery and obtaining of the remaining incrusting materials of the plant tissues.

RALPH MALCOLM HIXON. CHARLES JAMES PETERSON. CHESTER HAMLIN 

